It's from the Simpsons Treehouse of Horror VII. The aliens Kang and Kodos abduct Bill Clinton and Bob Dole just before the 1996 election and use a bioduplication machine to take their places. Homer manages to expose their plot just before the election, but Kodos states, "It's true, we are aliens. But what are you going to do about it? It's a two-party system; you have to vote for one of us."

Kang gets elected and proceeds to enslave the human race. The Simpsons end up being put to work and Marge says, "I don't understand why we have to build a ray gun to aim at a planet I never even heard of." Homer replies, "Don't blame me, I voted for Kodos!"